Recently, a variety of terahertz range modulation components have been studied and invented with the development of the terahertz range. In past studies, the phase shifter was made of the nematic liquid crystal, which has large birefringence, and the direction of the nematic liquid crystal was changed by adjusting the electric field to change the refractive index as the phase modulation.
In more detail, the phase shifter is made of the nematic liquid crystal, the magnetic field or electric field is used to change the direction of the nematic liquid crystal resulting in a change of the refractive index. The substrates of the liquid crystal phase shifter are mostly made of quartz glass, wherein the quartz has an effect of being highly transparent in the visible light frequency range and the terahertz frequency range. The electrodes need be disposed and have a voltage applied to achieve the birefringence by changing the refractive index of the liquid crystal. The most common method is that a transparent conductive electrode, such as indium tin oxide (ITO) thin film, is plated on the quartz glass to be the electrodes because the quartz glass is not conductive.
However, ITO thin film is transparent in the visible light frequency range, but has a high absorption in the terahertz frequency range and cannot be transparent. Thus, ITO thin film is a material with low transparency and high absorption in the terahertz frequency range, and the effect of the liquid crystal phase modulation of the liquid crystal phase shifter is poor.
As a result, it is necessary to provide a silicon based terahertz full wave liquid crystal phase shifter to solve the problems existing in the conventional technologies, as described above.